JP7619901B2 - Threshold Setting System - Google Patents

Description

The present invention relates to a threshold setting system that automatically sets the threshold used to determine whether a person is seated.

In machine tools such as lathes, a workpiece is held in a spindle chuck, and a cutting tool is placed on the workpiece as the spindle rotates to perform cutting processing. If the workpiece does not come into accurate contact with the seating surface of the spindle chuck, excessive cutting of the workpiece will occur, resulting in a decrease in the quality of the finished product. Therefore, machine tools are provided with a workpiece seating determination device to determine whether the workpiece is properly seated on the seating surface of the spindle chuck. Specifically, a detection hole is formed in the seating surface of the spindle chuck, and air is sent into the hole from an air supply source. The workpiece held by the spindle chuck is placed on the seating surface and blocks the detection hole, but a small gap is created, allowing a certain amount of air to leak, and seating determination is made based on the amount of air leaked.

In seating judgment, the amount of air leaking out from the gap between the workpiece and the seating surface is measured and compared with a preset threshold value to make a seating judgment. To set such a threshold value, a master work for checking air pressure that creates a specified gap on the seating surface of the workpiece is used. The master work has an adjustment groove formed to create a certain amount of air leakage. For example, the following Patent Document 1 discloses a master work that focuses on the fact that the amount of air leaking from the gap changes depending on the roughness of the workpiece surface. The master work is configured so that a screw is provided that protrudes from the bottom of the adjustment groove that creates air leakage, and the size of the gap can be adjusted according to the amount of protrusion of the screw.

JP 2017-024090 A

When machine tools repeatedly process workpieces, the seating surface becomes dirty due to the generated cutting chips and scattered coolant, which deteriorates the condition of the detection hole. This can change the amount of air leaking from the detection hole, making it necessary to reset the threshold periodically. However, in the process of setting the threshold, the detection hole and the adjustment groove of the master work must be aligned, so phase determination is required when mounting the master work, which can be cumbersome for some workers. Furthermore, because the dirt on the seating surface varies depending on the processing content, the threshold resetting work is not performed frequently, but checking for dirt is also cumbersome, and it is a task that is easily forgotten if a long period passes until the next reset.

Therefore, the present invention aims to provide a threshold setting system that automatically resets the threshold for seating determination in order to solve such problems.

The threshold setting system according to the present invention includes a machine tool having a detection hole formed in the seating surface of a spindle chuck that grips a workpiece and a seating determination device that measures the amount of air leaking from the detection hole with a flow measuring device, an automatic work transfer machine that transfers the workpiece between the spindle chuck and the machine tool, a master workpiece having an adjustment groove formed therein that creates a predetermined gap on the seating surface when gripped by the spindle chuck, and a control device that executes a phase determination process for aligning the detection hole with the adjustment groove for the machine tool and the automatic work transfer machine, a transfer process for transferring the master workpiece to the spindle chuck, and a threshold calculation process for calculating a threshold for seating determination based on the amount of leakage measured by the flow measuring device.

According to the above configuration, the master workpiece is transferred to the spindle chuck, which has had the phase of the detection hole aligned with the adjustment groove by the automatic workpiece transport machine, and air is supplied toward the detection hole, releasing the air and causing a predetermined amount of air leakage. The amount of leakage is measured by the flow meter, and the threshold value for seating determination is automatically calculated and set based on the measured amount of leakage.

FIG. 2 is a side view showing the internal structure of the machine tool. FIG. 1 is a simplified diagram illustrating a state in which an automatic workpiece transport device transfers a workpiece to a machine tool. FIG. 2 is a diagram showing a simplified configuration of a seating determination device; FIG. 4 is a diagram showing the seating surface of the spindle chuck. FIG. 2 is a perspective view showing a master work. FIG. 2 is a perspective view showing a master placement stage for placing a master work. FIG. 2 is a block diagram showing a control system of the machine tool. FIG. 11 is a flowchart showing the execution of a threshold setting program.

One embodiment of the threshold setting system according to the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing the internal structure of a machine tool. The machine tool 1 is mounted on a movable bed 2 equipped with wheels, and can move in the forward and backward directions (Z-axis direction) along rails laid on a base 3. The machine tool 1 has a tool table 11 equipped with rotating tools such as an end mill or drill, or cutting tools such as a cutting tool, and is provided with a turret device 4 capable of rotating and indexing the tool table 11.

The machine tool 1 has a structure in which a spindle unit 5 is mounted on a movable bed 2 and a spindle chuck 12 that grips a workpiece is rotatable. The machine tool 1 is a two-axis lathe in which a turret unit 4 is moved by a Z-axis drive unit 6 that moves the turret unit 4 in the Z-axis direction parallel to the spindle, and an X-axis drive unit 7 that moves the turret unit 4 in the X-axis direction, which is the vertical direction of the machine body. The Z-axis drive unit 6 and the X-axis drive unit 7 have a slidable Z-axis slide 13 or X-axis slide 14, and are configured to convert the rotational output of a servo motor into linear motion by a ball screw mechanism.

In addition to the machine body cover 15 that constitutes the machining chamber 10, the machine tool 1 is provided with an openable front cover 16 at the front of the machine body. The machine tool 1 is modularized like other work machines that constitute the machining machine line, and a work transport space 20 is formed by arranging multiple front covers 16 in the machine body width direction. As shown in Figure 2, an automatic work transport machine 8 that transfers the work W is incorporated in the work transport space 20. Figure 2 is a simplified diagram showing the state of the automatic work transport machine 8 when transferring a work to the machine tool 1.

The automatic work transport machine 8 is composed of a traveling device 18 that moves the traveling platform 21, and a work transport robot 19 mounted on the traveling platform 21. The work transport robot 19 is configured so that the form of the upper arm member 23 and the forearm member 25 can be changed by driving the first joint mechanism 24 and the second joint mechanism 26. Specifically, the upper arm member 23 and the forearm member 25 can be transformed into a compact moving posture in which they are folded and erected, and into a working posture in which they are extended and inclined forward as shown. In the automatic work transport machine 8, a robot hand 27 equipped with a chuck mechanism is attached to the tip of the work transport robot 19, making it possible to grip and release the work W.

The workpiece transport robot 19 enters the machining chamber 10 by opening the sliding door of the machine cover 15, and transfers the workpiece W to the spindle chuck 12. The machine tool 1 is provided with a seating determination device that determines whether the received workpiece W is properly gripped by the spindle chuck 12. FIG. 3 is a simplified diagram showing the configuration of the seating determination device 17 provided in the machine tool 1, and FIG. 4 is a diagram showing the seating surface of the spindle chuck 12. The seating determination device 17 has detection holes 32 formed in three locations on the same circumference at intervals of 120 degrees on the seating surface 31 of the spindle chuck 12. An air supply source 34 such as a compressor is connected to the three detection holes 32 via an air supply pipe 33. An electromagnetic opening/closing valve 35, a pressure control valve 36, and a flow rate measuring device 37 are connected to the air pipe 33 in this order.

In the seating determination device 17, air sent from the air supply source 34 to the air pipe 33 flows to the spindle chuck 12 at a predetermined pressure, and is released from the detection hole 32 in the unclamped state. When the workpiece W is delivered from the workpiece transport robot 19 to the spindle chuck 12, the detection hole 32 is blocked and the flow of air is cut off. However, if there is a small gap, air leakage will occur. In the seating determination device 17, the amount of leakage is measured by the flow rate meter 37, the measured value is sent to the control device 9, and seating determination is made by comparing it with a preset threshold value.

When the machine tool 1 repeatedly processes a workpiece, chips and coolant scattered in the machining chamber adhere to the detection hole 32 of the spindle chuck 12, obstructing the air flow and causing changes in the amount of air leakage. Even in such cases, it is necessary to perform stable and accurate seating determination, and it is necessary to periodically reset the threshold value according to changes in the amount of leakage. Therefore, in this embodiment, a threshold setting system is configured that makes it possible to reset the threshold value by controlling the machine tool 1 and the automatic workpiece transporter 8.

To set the threshold value, a master workpiece MW is used that creates a predetermined gap on the seating surface 31 of the spindle chuck 12. The master workpiece MW is gripped by the chuck jaws with its center aligned on the seating surface 31 as shown by the dashed line in FIG. 4. FIG. 5 is a perspective view showing the master workpiece MW. The master workpiece MW has a positioning hole 41 formed in the center of a cylindrical member, and a first adjustment groove 43 and a second adjustment groove 44 formed at positions 180 degrees apart on the axial end face, extending radially from the positioning hole 41 to the outer diameter end. Furthermore, a phase determination hole 42 is formed at a position away from the positioning hole 41 to keep the phase constant when the master workpiece MW is handled.

The first adjustment groove 43 and the second adjustment groove 44 virtually create a gap when the workpiece is gripped by the spindle chuck 12 and placed against the seating surface 31. The two grooves have different depths, and the first adjustment groove 43 is a shallow OK groove that creates an acceptable gap when the workpiece is seated, with a depth of, for example, about 0.03 mm. The second adjustment groove 44 is a deep NG groove that creates a gap that is determined to be a seating error, with a depth of, for example, about 0.05 mm. When determining the leakage amount (threshold value) that is determined to be appropriate seating, the first adjustment groove 43 and the second adjustment groove 44 are overlapped in order with respect to the three detection holes 32 in the seating surface 31. Therefore, the master workpiece MW needs to be gripped in a constant phase state with respect to the spindle chuck 12.

Here, FIG. 6 is a perspective view showing a master placement stage 45 for placing the master work MW. The master placement stage 45 has a positioning pin 47 and a phasing pin 48 stuck into a flat plate 46. The positioning pin 47 is a cylindrical member with a diameter corresponding to the positioning hole 41 of the master work MW, and the phasing pin 48 is a cylindrical member with a diameter corresponding to the phasing hole 42. The positioning pin 47 and the phasing pin 48 are formed so that the positional relationship between the positioning hole 41 and the phasing hole 42 of the master work MW coincides.

As shown in FIG. 6, the master workpiece MW is placed on the master placement stage 45 so that the positioning hole 41 fits over the positioning pin 47 and the phase determination hole 42 fits over the phase determination pin 48. The master placement stage 45 is provided within the movement range of the workpiece transport robot 19, for example, midway through the workpiece transport space 20 in which the workpiece transport robot 19 moves, or at the workpiece input or output section of the line. Therefore, by having the workpiece transport robot 19 take out the master workpiece MW at any timing, it is possible to automatically set a threshold value for the seating determination device 17 of the machine tool 1, etc.

The machining line is provided with multiple work machines, such as a machine tool 1, and an automatic work transporter 8 that transports work pieces to each work machine, and a control communication network is constructed that enables the exchange of command signals between the control device on the work machine side, such as the control device 9 of the machine tool 1 shown in FIG. 1, and the control device provided on the automatic work transporter. In the threshold setting system of this embodiment, a threshold setting program is stored in the control device 9 of the machine tool 1, and the threshold setting is performed by driving and controlling the machine tool 1 and the automatic work transporter 8.

Figure 7 is a block diagram showing the control system of the machine tool 1. The control device 9 is mainly a computer equipped with storage devices such as a ROM 52, a RAM 53, and a non-volatile memory 54 in addition to a CPU 51, and is connected to each drive unit such as the turret unit 4, the spindle unit 5, the Z-axis drive unit 6, the X-axis drive unit 7, and the seating determination unit 17 via an I/O 55. In addition, the machine tool 1 has an operation display unit 58 attached to the front of the machine body, which displays work information and an operation screen, and allows the operator to input settings, and is connected to the control device 9. The control device 9 stores processing programs for various types of processing, workpiece types, and workpiece processing information related to tools and jigs in a memory unit. In particular, in this embodiment, a threshold setting program is stored.

Figure 8 is a diagram showing a flowchart for executing the threshold setting program. The threshold resetting is programmed to be performed, for example, once a month, so that it is automatically started on a set date in conjunction with a calendar function. In addition, since the degree of contamination of the spindle chuck 12 varies depending on the machining content, the operator can press the start button on the operation display device 58 to start the threshold setting program at any time.

When the threshold setting program is started, first, the master work MW is taken out from the master table 45 by the work transport robot 19 in the automatic work transport machine 8 (S101). In addition, the phase of the detection hole 32 in the spindle chuck 12 is determined in the machine tool 1 (S102). The master work MW on the master table 45 is in a fixed state, and the spindle chuck 12 performs phase determination for the master work MW transported in that state. Then, when the master work MW is transferred between the work transport robot 19 and the spindle chuck 12, the first adjustment groove 43 and the second adjustment groove 44 are positioned as shown in FIG. 4, and one of the three detection holes 32 is overlapped with the second adjustment groove 44, which is an NG groove (S103).

Air is constantly blowing out of the three detection holes 32, but air leaks from the first detection hole 32 that is overlapped with the second adjustment groove 33, while the other detection holes 32 are blocked. The amount of leakage in this situation is measured by the flow meter 37 and stored in the memory of the control device 9 as the measurement value NG1 at the first detection hole 32 (S104). After that, the master workpiece MW is removed from the spindle chuck 12 by the work transfer robot 19 (S105), and it is confirmed whether the measurement and storage of the amount of leakage from the three detection holes 32 has been completed (S106). Since it is still the first detection hole 32 (S106: NO), the process returns to step S102, the spindle chuck 12 is rotated 120 degrees, and the phase is determined so that the second detection hole 32 is overlapped with the second adjustment groove 44, which is the NG groove.

Then, steps S103-S106 are repeated. That is, the master workpiece MW is transferred to the spindle chuck 12, the amount of air leakage blowing out from the second detection hole 32 superimposed on the second adjustment groove 33 is measured, and the measured value NG2 is stored in the memory unit. After that, the master workpiece MW is removed from the spindle chuck 12, it is confirmed that the processing is for the second detection hole 32, and the process returns to step S102 (S106: NO). Next, steps S103-S106 are repeated for the third detection hole 32, and the measured value NG3 of the leakage amount is measured and stored in the memory unit. When the processing of the third detection hole 32 for the NG groove is completed (S106: YES), the process moves to the processing for the OK groove.

Next, the processing for the OK slot is performed in the same manner as for the NG slot. First, the spindle chuck 12 is phased so that the first detection hole 32 is overlapped with the first adjustment groove 43 of the OG slot shown in FIG. 4 (S107), and the master workpiece MW is transferred there from the workpiece transport robot 19 (S108). Because air is blowing out of the detection hole 32 through the first adjustment groove 43, the leakage amount is measured for the first detection hole 32, and this value is stored in the memory as the measured value OK1 (S109). After that, the master workpiece MW is removed from the spindle chuck 12 (S110), and it is confirmed whether the measurement and storage of the leakage amounts for the three detection holes 32 has been completed (S111).

Until the processing for the third detection hole 32 is performed (S111: NO), steps S107-S111 are repeated in order for the second and third detection holes 32, and the respective leakage amounts are stored in the memory as measured values OK2 and OK3. Then, when the processing for the third detection hole 32 for the OK groove is completed (S111: YES), the threshold value is calculated based on the following formula (S112). The threshold value TH is calculated by TH = OKa + (NGa + OKa)/2, assuming that the average values of the leakage amounts in the NG groove and OK groove of the three detection holes 32 are NGa = (NG1 + NG2 + NG3) / 3 and OKa = (OK1 + OK2 + OK3) / 3. In other words, the intermediate value between the leakage amounts in the NG groove and the OK groove is set as the threshold value TH.

After completing the threshold setting process, the master work MW is returned to the master table 41. The master work MW held by the robot hand 27 is in the same state as when it is attached to the spindle chuck 12, that is, the positions of the first adjustment groove 43 and the second adjustment groove 44 are the same. Therefore, by returning the master work MW to the master table 45 as it is, the positioning hole 41 of the master work MW is always aligned with the position of the positioning pin 47, and the phase determination hole 42 is always aligned with the position of the phase determination pin 48, as shown in FIG. 6.

Therefore, according to this embodiment, the threshold for the seating determination device 17 can be automatically set by controlling the machine tool 1 and the automatic work transporter 8 in accordance with the threshold setting program stored in the control device. This eliminates the need for the operator to perform tedious work, and by inputting the execution time, the threshold is periodically reset, so that seating determination is always performed using a stable threshold.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the present invention.
In the above embodiment, the resetting of the threshold value was described. However, for example, the initial setting performed after cleaning the detection hole 32 can be executed by an operator pressing the start button on the operation display device 58 to start up the threshold setting program.

Reference Signs List 1...machine tool 8...automatic workpiece transport machine 12...spindle chuck 17...seating determination device 31...seating surface 32...detection hole 37...flow rate measuring device 41...positioning hole 42...phase determination hole 43...first adjustment groove 44...second adjustment groove 45...master placement table 47...positioning pin 48...phase determination pin MW...master workpiece

Claims (7)

a machine tool having a seating determination device in which a detection hole is formed in a seating surface of a spindle chuck that grips a workpiece, the machine tool being equipped with a seating determination device that measures an amount of air leakage flowing out from the detection hole with a flow rate measuring device;
an automatic workpiece conveyor that delivers the workpiece to and from the spindle chuck;
a master workpiece having an adjustment groove formed therein for generating a predetermined gap on the seating surface when the master workpiece is gripped by the spindle chuck;
a control device that executes, for the machine tool and the automatic workpiece transporter, a phase determination process for aligning the detection hole with the adjustment groove, a transfer process for transferring the master workpiece to the spindle chuck, and a threshold calculation process for calculating a threshold for seating determination based on the amount of leakage measured by the flow rate measuring device;
A threshold setting system having: The threshold setting system according to claim 1, wherein the detection holes are formed on the same circumference of the seating surface, and the master work is formed with a shallow first adjustment groove that creates an acceptable gap when the work is seated, and a second adjustment groove that is deeper than the first adjustment groove and creates a gap that is determined to be a seating error. The threshold setting system according to claim 2, wherein the control device sequentially phases the plurality of detection holes with respect to the first adjustment groove and the second adjustment groove, and calculates the threshold based on the respective leakage amounts measured by the flow rate measuring device. The threshold calculation process calculates a first average value of the leakage amount occurring in each of the multiple detection holes phased to the first adjustment groove and a second average value of the leakage amount occurring in each of the multiple detection holes phased to the second adjustment groove, and sets the threshold value to a value obtained by adding the average of the first average value and the second average value to the first average value. The threshold setting system according to claim 2 or 3. The threshold setting system according to any one of claims 1 to 4, wherein the master work has a positioning hole formed at the center of a cylindrical member and a phase determination hole formed at a position away from the positioning hole. The threshold setting system according to claim 5, wherein the first adjustment groove and the second adjustment groove of the master work are formed at positions 180 degrees apart on the axial end face from the positioning hole to the outer diameter end in the radial direction. 7. The threshold setting system according to claim 5, wherein the master work is placed so as to fit onto a master stage having positioning pins and phase determination pins corresponding to the positioning holes and the phase determination holes, and the master stage is disposed at any position from which the master work can be removed by the automatic work transport machine.

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